1. Field of the Invention
This invention relates to a graphite rotary tube furnace for the high temperature treatment of various materials in an inert atmosphere.
2. Prior Art
The processing of materials at very high temperatures, for example, at temperatures of from about 1500.degree. C. to temperatures as high as 3000.degree. C. or higher presents a number of problems that must be overcome in the design of the process equipment to be used. Firstly, the choice of construction materials is limited. Graphite is often the material of choice when extreme temperatures are used. Such elevated temperatures frequently require that the treatment be carried out in an inert atmosphere, for example, a non-oxidizing atmosphere to avoid undesired reactions with the material being processed. In addition, when the equipment is constructed of graphite, the material of construction itself may react with the oxygen in air at extremely high temperatures. Thus it may be necessary, or preferable, to provide an inert atmosphere enveloping the graphite equipment as well as the material being processed. In the case of moving equipment, such as the graphite rotary tube furnace of the present invention, the maintenance of an inert atmosphere both within the tube and surrounding the graphite tube during operation presents particular difficulties.
The use of graphite in tubular reactors is known in the literature. U.S. Pat. No. 3,656,910 to Ferment discloses a graphite tube furnace for the production of carbonaceous fibrous material.
U.S. Pat. No. 5,144,108 to Passarotto discloses a rotating tube furnace having interior rotating paddles to aid in the transit of material through the tube.
U.S. Pat. No. 4,988,289 to Coucher discloses a reaction furnace comprising a rotating core within a heated shell. Blade segments in side of the tube are arranged in a helical pattern to aid in the moving of materials through the tube.
U.S. Pat. No. 5,251,231 to Croker et al. discloses a furnace having a cooling fluid (water) surrounding the entire furnace.
U.S. Pat. 5,393,225 to Freiberger et al. discloses a rotating tubular kiln comprising a replaceable rotating tube surrounded by a tubular jacket and separated therefrom by a gap.
There remains a need for an improved rotary furnace or kiln suitable for the treatment of particulate materials at very high temperatures in a controlled atmosphere.
It is an object of the present invention to provide a graphite rotary tube furnace suitable for continuous operation at temperatures up to 3000.degree. C. or higher.
It is a further object of the invention to provide a high performance ultra high temperature rotary tube furnace utilizing conveniently replaceable components.
It is a still further object of the invention to provide a mechanically driven graphite rotary tube furnace wherein both the product being treated and the furnace components may be contained in a controlled atmosphere at high temperatures while the furnace is rotated.
A still further object is to provide a graphite rotary tube furnace characterized by excellent thermal efficiency and capable of providing single or multiple temperature control zones.
It is a further object to provide a rotary tube furnace capable of operating at high temperature wherein radiation heat loss at the ends of the tube is minimized.